you're off to a bad start. Xiaomi is not officially supported but can work. I have a bag of about 25 devices I had to remove, buttons, sensors motion & flood. They were wreaking havoc on my zigbee mesh. Much better since those are now disconnected. You can get zigbee 3.0 devices(tuya, sonoff) for the same price and they generally are more reliable, as they follow zigbee specs, xiaomi does not follow zigbee standards.
Some folks here claim to have zero issues with Xiaomi, I'm not one of them
Thanks Mark! I’ve read this before but was not able to do it.
I guess it worked better by keeping the button pressed and then pressing the reset pin.
It blinked 3 times and was immediately found by the HE but again got stuck at “initialising”.
After that I hit search for new Zigbee devices again and repeated the same procedure. It then discovered a LUMI device with the save button enabled.
Changed the device type to Xiaomi Button and Voilá!